When you pull up to the pump to buy gas, you are presented with choices.The octane rating of a fuel is the thing we see on the pump. 87, 89, 91, 93 and even 94 in some places.
What is Octane? Octane is a hydrocarbon that occurs as part of the gasoline refining process. It has 18 different popular variants that include combinations with Heptane, Hexane, Pentane and Butane. For the purposes of motor fuels Octane is the measure of resistence to ignition under pressure. So the higher the Octane number the greater the temperature at which it allows the fuel to release it's energy. Octane rating is not a measure of the energy contained in the fuel, just the temperature at which it goes BANG!
So, you won't get any more power from 91 Octane fuel unless your engine is optimized to take advantage. In fact, if you have a low compression engine and use 91 Octane fuel, you may actually get less performance, since the engine has to work harder to ignite the fuel.
What else is in gasoline? There are detergents, solvents, temperature stabilizers, proprietary additives and in most fuels Ethanol. Depending on your geographical location, your refiner may change your fuel formula several times a year to compensate for temperature and other environmental factors. Summer fuel has anti vapour lock additives and winter fuels are adjusted for lower temperatures etc.
Ethanol: The double edged sword. On one hand, adding ethanol makes gasoline burn cleaner, on the other it produces less energy than gasoline,(less BTU's per volume), so you use more. Pure Ethanol has higher Octane than gas (about 110), but once it's blended with gasoline the number on the pump is what it is. Remember Octane rating is not potential energy. Ethanol has some other less than desirable qualities. It is Hygroscopic, it attracts water. This is particularly a problem for seasonal and marine engines. Engines in storage for long periods can actually form biological growths in the fuel system (gunk,varnish, slime) and cause damage to organic gaskets and rubber components. Fuel stabilizers can help some, but they are only effective for a few months and must be well mixed with the stored fuel. Fuel stabilizers can possibly cause emission test failures (tailpipe emission tests) and should be run out of engines before testing.
Typically, gasoline (in Canada) has 10% ethanol in 87 fuel, 5% in 89 fuel, and 0% in 91 or higher Octane fuel.
I understand, on the west coast US those numbers are higher. So we generally only use premium in our recreational and seasonal equipment.
All major refiners produce about the same fuels. Gasoline comes out of the refinery as regular or premium fuel, and the additive packages are added as it is loaded for delivery. At your local gas station, there are usually two tanks, or sets of two, one for regular and one for premium, and it is mixed at the pump depending on your choice. Why is premium so much more money than regular. Well, aside from the fact we're being hosed at the pump, they sell a lot less premium fuel. Racing gas is a whole different discussion, is very unstable and must be kept out of direct sunlight or it can start to separate in hours. It's also expensive. With the Trans Am cars, we typically blew through $500 a weekend in fuel. (2+ fill ups 22 gallon fuel cell)
You know what they say;"If you want to make a small fortune in racing, best to start with a large fortune.
Questions, comments, likes? Good day all!